Method and apparatus for twist plied yarn and product thereof

ABSTRACT

A pretwist memory-free, plied, bulked, continuous filament yarn and a method and apparatus for producing the same in one continuous operation are disclosed. In the method, a first single end of yarn having no more than a producer&#39;&#39;s twist is ballooned about and plied with a like second single end of yarn while both are under tension and advancing at a common linear speed. A somewhat higher tension is utilized during the plying operation to maintain a stable balloon. The plied yarn is then subjected to heat while the tension is relaxed, followed by a cooling and drying stage, to enable the yarn to be twist-set in a bulked condition, with the component single ends substantially free of any twist memory. This abstract is not to be taken either as a complete exposition or as a limitation of the present invention, however, the full nature and extent of the invention being discernible only by reference to and from the entire disclosure.

[ June 28, 1974 United States Patent [191 Clarkson METHOD AND APPARATUS FOR TWIST Primary Examiner-John Petrakes PLIED YARN AND PRODUCT THEREOF [57] ABSTRACT A pretwist memory-free, plied, bulked, continuous filament yarn and a method and apparatus for producing the same in one continuous operation are disclosed. In the method, a first single end of yarn having no more [22] Filed: May 25, 1973 [21] Appl. No.: 363,986 than a producers twist is ballooned about and plied with a like second single end of yarn while both are under tension and advancing at a common linear [52] US. 57/34 HS, 57/58.3, 57/157 TS [51] Int.

speed. A somewhat higher tension is utilized during D02g 1/00 58.3 57/58.38, 157 TS the plying operation to maintain a stable balloon. Th

[58] Field of 57/34 5 plied yarn is then subjected to heat while the tension is relaxed, followed by a cooling and drying stage, to enable the yam to be twist-set in a bulked condition, with the component single ends substantially free of [56] References Cited UNITED STATES PATENTS any twist memory. This abstract is not to be taken eie 0 h m t m w 0 dr. .w n e la h a r C .1 r y m I lay an].

I n mm mam n mm o u r s .16 0 a d Pw b X e n .1 e 6 r f m m P m e m fie o w nh C e n mmee n 2. mm, E mm w .l C BRBSG 900922 56677 99999 HHHHH 45 26 40307 05 3288 008236 ,3 23333 15 Claims, 3 Drawing Figures SHEEI 2 0f 3 PATENTED I74 1 METHOD AND APPARATUS FOR TWIST PLIED YARN AND PRODUCT THEREOF BACKGROUND OF THE INVENTION The present invention relates generally to thefabrication of tuftingyarn utilized in the manufacture of shag carpeting and. the like. More-particularly, the present invention relates to a method of and apparatusfor producing plied, bulked, continuousfilament yarn in one continuous operation wherein .single ends of yarn are plied with one another-and twist-set in abulked condition.

The fabrication of tufting' yarn for shag. carpeting and the like is conventionally effected by a batch process in which single ends of yarn are. joined to one another and processed in a number of independent and discontinuous steps. The stepsof this process in'generalaarez (a) twisting each single end of yarn about its ownlongitudinal axis, for example to the extent of 3 turns per inch in the Z direction; (b) plying the twistedsingle ends with one another with an equal amount of twist. but in the opposite, i.e., the S, direction, so that the initial Z twist is removed. from each ofthe single ends; skeining the plied yarn by winding the latter on a swift; (d) tumblingthe plied yarnin the presence ofmoist heat, e.g., steam at atmosphericpressure,.todevelop the inherent bulk in the yarn; (e) twist-setting the'plied yarn in an autoclave wherein theyamis subjectedto high-temperature pressurized steam; (f) drying: the yarn in the presence of dry-heat; and (g) deskeiningthe yarn and winding'it upon .a tube- One of the disadvantages of this batch processis the need for the above-recited numerous and time consuming steps -fortreating the yarn after the startingends have been plied to one another. Moreover, the initialtwisting of thesingleends of yarn independently of one another before they are plied togetherleads to another disadvantage. When the pre-twisted single ends are plied to one another, with a ply twist generally equal but opposite in direction to the singles twist, they should lose the previously imparted twist and return to the producers twist; i.e., a twistofvirtuallyzero. However, since each single end ofyarn, after havingzbeen given its initial twist, is normally stored for a period of time, often many hours, prior to being plied, the single ends develop a memory anda tendency to revert back to the initial twist after the plyingxoperation. Thus, the single ends which form the plied yarn, tend toflare or separate from one another rather thanremain ina predictable twistfretentive condition necessary for high quality shag carpeting unless they are twist-setat a high temperature. Such high temperature. twist-setting. tends to affect the uniform dyeability of the plied yam.

SUMMARY OF THEINVENTION Accordingly, it is a primary'object of the present in vention to provide a novel method of and apparatus forproducing plied, bulked, continuous filament yarn in a mannerenabling the disadvantages and drawbacks of the. known processesand.apparatusesofthis type to be efficaciously avoided.

It is another object of the present-invention to provide such a method which can be carried out in one continuous-operation and also obviates the necessity of first twisting the singleends of yarn in one direction prior to plying them to one another and then performing the plying operation with a twist in the opposite di- It is still a further object of the present invention to greatly simplify and reduce the number of process stepsnecessary for treating the plied yarn after the single ends have been joined to one another.

It isstill another object of the present invention to optimize the development of bulk and dyeability in the plied yarn by twist-setting the plied yarn in the presence of either dry or moist heat and under relaxed tensron.

Generally speaking, the objectives of the present invention are achieved through the use. of an apparatus in which, in one continuous operation, generally untwisted single ends of bulked continuous filament yarn are first plied to'one another by a ballooning of one end about the other while both are advanced under tension and at a common linear velocity to form a twistretentive'plied'array, and the resultant plied yarn is then advanced while under relaxed tension first through a heating zone in which the plied yarn is twistset in a bulked condition, and then through a cooling and'drying zone preparatory to being. wound into a package. Since, in the practice of the present invention, the twist, setting temperature does not have to be high enough to overcome the memory of an initial singles twist, such temperature may be somewhat lower than has been the case in the conventional process.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings in greater detail, the apparatus according to the preferred embodiment of the present invention comprises, in series, a first yarn supply station 4, a second yarn supply station 5, a ballooning station 6 in which the second yarn supply station 5' is disposed, a twist-setting station 7 having both a'heatingzone and a cooling and drying zone, anda take-up station 8;

The'first'yam supply station 4 includes means for supporting a yarn package 10 from which a single end of yarn 11 is to be drawn for advancement to the ballooning station 6. To guide the yarn 11 along this portion of its movement, there are provided pigtail guides 9and 9', a set of friction or tensioning discs 12, and

pigtail guides 14, 15 and 16. Downstream of the pigtail guide 16, there isprovided apairof rolls l7 andl8 mounted'on a stationary housing 74 at the exterior thereof for rotation about parallel axes; The roll 18, which has a lesser diameter section 18' and agreater diameter section 18", is rotatably driven at a predetermined constant rate by any suitable means (not shown) located in the housing 74, while the roll 17 is an'idler roll. The roll 18 is provided on both sections thereof with a high friction surface, e.g., by means of a coating of a slippage-preventing material such as aluminum oxide or the like. A second idler roll 17 is arranged coaxially with the roll 17 but is independently rotatable. The yarn 11, as shown in FIGS. 1 and 2, preferably is passed several times about the pair of rolls 17 and 18' and then continues on its way to the ballooning station 6. To guide the yarn along this portion of its movement, there are provided pigtail guides 19, 20 and 21.

The ballooning station 6 includes a pot 80 which is located above the housing 74 and incorporates the second yarn supply station 5, i.e., the location of a yarn package 30 from which a second single end of yarn 31 to be plied with the yarn 11 can be drawn. Arranged atop the pot 80 is a spindle or stub shaft 76 rotatably supporting a flier 22 provided with a pair of oppositely directed, counter-balancing arms each of which terminates in a respective yarn guide or pigtail 23. The previously mentioned pigtail guide 21 is disposed on the axis of rotation of the flier 22.

Referring now in particular to FIG. 2, arranged below the pot 80 is a horizontal rotatable plate 24 which is fixedly secured above the housing 74 to a rotatable hol- I low shaft or spindle 58 journaled in the housing with the aid of suitable bearings (not shown). The plate 24 is rotated in the direction of arrow 50 by means of a drive assembly (shown in FIG. 2 only) including a motor 52, a first pulley 53 secured to the motor shaft 52, a second pulley 56 secured to the bottom end of the spindle 58, and a belt 54 drivingly connecting the pulley 53 to the pulley 56. The plate 24 is provided at one point adjacent its peripheral edge with a yarn guide aperture 81 (see also FIG. 1) and the spindle 58 is provided between the plate 24 and the housing 74 with a radially directed passageway 57 (FIG. 2). From the pigtail guide 21, therefore, the yarn 11 passes through the yarn guide 23 of the flier 22 and the guide aperture 81 in the plate 24, into the radial passageway57 in the spindle 58, and thence into the hollow interior 58' of the spindle 58.

Reverting now to the pot 80, the latter is provided in its interior with conventional means 82 and 83 for centering and supporting the yarn package 30. Also arranged internally of the pot 80 is a flier 84 which is in the form of an L-shaped arm having a horizontal portion 84a freely rotatably journaled adjacent one end thereof on the spindle or stub shaft 76. The flier 84 thus can rotate independently of the external yarn flier 22. The flier 84 is provided generally medially of the portion 84a thereof with a slot 85 and in the vertically disposed portion 84b with an elongated passageway 86. The portion of the spindle 76 located within the pot 80 is provided with an axial passageway 87 and a radial passageway 88. The yarn 3l,'when being drawn off the package 30, thus moves through the passageways 86 to 88 and the slot 85; During such movement, the yarn 31 is subjected to friction and tension as it slidably engages various portions of the flier 84. From the passageway 88, the yarn path in the pot 80 runs to an exit aperture 89 from the pot via a yarn guide 90, thence via a pigtail 91 to a set of rolls 26 and 27.

As shown in FIG. 2, the pot 80 is supported by a second stationary housing 93 interposed between the plate 24 and the pot 80. For a reason'which will become clear presently, a portion of the shaft or spindle 58 extends upwardly beyond the plate 24 and into the housing 93 where that portion of the spindle is also journaled by means of suitable bearings (not shown). Inasmuch as the housing 93 is supported only by the spindle 58, a braking device (shown in FIG. 2 but omitted from FIG. 1 for the sake of simplicity) is provided to inhibit rotation of the housing 93 and pot 80 with the spindle 58 and plate 24. In the illustrated form of the apparatus, the braking device includes a magnet 71 adjustably mounted at 73 on a beam or like member 94 of the framework supporting the housing 74 and a second magnet 72 mounted on an arm or like adjunct 77 of the housing 93, the magnets being spaced from one another sufficiently to straddle and leave unobstructed the path of movement of the yarn 11 from the flier 22 to the plate 24.

Also mounted on the housing 93 for rotation about parallel axes are the said rolls 26 and 27. Of these, the roll 26 is rotatably driven by any suitable means (not shown) located in the housing 93, at the same rate of rotation as the roll 18, while the roll 27 is an idler roll. As in the case of the yarn 11 at the. rolls l7 and 18, the yarn 3l is preferably passed several times about the pair of rolls 26 and 27, and the former of these, like the roll 18 is provided with a high friction slippagepreventing surface. The diameter of the roll 26 is equal to that of the section 18' of the roll 18, so that the linear speed of movement of the yarn 31 is the same as that of the yarn 11. From the idlerroll 27, the path of movement of the yarn 31 goes through a transverse passageway (FIG. 2) disposed at the top of the frame 93 and thence into the top end of the portion of the hollow spindle 58 located in the housing 93, toward the entry location 57 of the yarn 11.

With respect to the driving of the rolls 18 and 26, it will be understood that this may be achieved in any suitable fashion. Merely by way of example, however, the actual arrangement (not shown) used in the illustrated apparatus includes a pair of sleeve or like annular gears carried by and rotatable with the spindle 58 in the housings 74 and 93, respectively, each such gear constituting a part of a respective gear train the last component of which is in direct driving relation to the shaft of the associated roll.

Freely rotatably journaled below the housing 74 is a preferably grooved idler roll 28 one side of which is shown as being located tangent to the axis of the spindle 58 and thus to the path of movement of the plied yarn 41 (formed, in a manner to be explained presently, from the ends of yarn 1 1 and 31) through and out of the spindle. From the roll 28 the plied yarn 41 is drawn to the heating zone of the twist-setting station 7 via pigtail guides 29 and 32, between which the yarn passes preferably several times around the pair of rolls l7 and 18".

In the operation of the section of the apparatus so far described, with the starting single ends of yarn 11 and 31 threaded into the apparatus as shown, both yarns are drawn from their respective packages 10 and 30 at the same predetermined constant linear speed by means of the rolls 18' and 26. The yarn paths unite at the plying station defined in the upper section of the rotating spindle 58. Since the plate 24 rotates at high speed with the spindle, the continuously advancing portion of the yarn 11 interposed between the guide 21 above the pot 80 and the guide aperture 81 in the plate 24 is revolved and ballooned around both the pot 80 and the second yarn supply station 5. Thus, the yarns 11 and 31 are laid upon one another and formed into a substantially twist-retentive, plied array 41 without being individually twisted at this stage, so that they re tain only the twist provided by the yarn producer.

The plied yarn 41 is drawn from the ballooning station by the larger diameter section 18" of the roll 18 at a somewhat higher linear speed than the feed-in rate of the starting yarns. This causes the plied yarn to be subjected to a tension somewhat greater than that to which the unplied yarns are subjected, whereby the plied yarn is stretched to a certain extent. The purpose of stretching the plied yarn is primarily to maintain a stable balloon. By stretching the plied yarn 41, therefore, a greater control over the manner in which the yarns 11 and 31 are laid upon one another is attained. It will be understood that the actual extent of stretching of the plied yarn 41 is solely a function of the relationship between the diameters of the rolls 18', 18'' and 26.

Referring now to FIGS. 1 and 3, the heating zone of the twist-setting station 7 comprises a closed cylindrical jacket 35 in which is fixedly mounted a pair of spaced, open-ended, parallel tubes 62 and 63. The jacket 35 is provided with suitable inlet and drain ports or fittings (not shown) for admission of steam into the jacket and extraction of condensate therefrom. A curved guide plate 61 is fixedly secured to the underside of the jacket 35 in juxtaposition to the bottom end openings of the tubes 62 and 63. Adjacent the upper end of the jacket 35 is arranged, on a suitable framework 95, a rotatable idler roll 33, and a further idler roll 34. The roll 34' is preferably provided with a high friction surface similar to those provided on the rolls l8 and 26.

The drying and cooling zone of the twist-setting station 7 comprises a pair of guide rolls 36 and 37 freely rotatably mounted on the framework 95, an idler roll 42 arranged coaxially with the roll 33, another idler roll 34" arranged coaxially with but having a somewhat smaller diameter than the roll 34', and a plurality of yarn or pigtail guides 38 and 39. The roll 42 is rotatable independently of the roll 33. The roll 34", however, is

integral and thus jointly rotatable with the relatively larger diameter roll 34' and, like the latter, has a high friction surface; In practice, the rolls 34' and 34" are different diameter sections of a single roll generally designated 34.

The winding or take-up station 8 includes, among other items not necessary to illustrate or describe herein, a guide bar 46 to which the yarn path from the roll 34" is defined by a pair of pigtail guides 44 and 45, a longitudinally reciprocally movable traversing rod 96 carrying a yarn guide 96, and a power driven roll 47, to enable the twist-set plied yarn, here denoted 51, to be properly wound onto a suitable core or tube 48 into the form of a package 49.

In operation, the plied yarn 41 emanating from the ballooning station 6 passes via pigtail guide 32 to and over the laterally aligned idler rolls 33 and 34' and moves thence downwardly into and through the heating tube 62. Upon emerging from the open bottom end of the tube 62, the yarn 41 passes over and around the guide plate 61 and then enters and moves upwardly through the second heating tube 63. The plied yarn 41 thus makes a double pass through the heating zone in which the twist-setting temperature is maintained preferably just below the softening or sticking point of the yarn material. The arrangement may be such that the yarn 41 will be subjected to dry heat, in which case the steam is not permitted to come in contact with the yarn, or that the yarn will be subjected to moist heat,

in which case the steam will be permitted to come in contact with the yarn. The twist-set plied yarn 51 emerging from the tube 63 then passes over the guide rolls 36 and 37 and thence via the pigtail guides 38 and 39 to and over the laterally aligned rolls 42 and 34", being cooled and, if necessary, dried during this interval. From the roll 34", the yarn 51 then moves to the guide bar 46 at the winding or take-up station 8.

It will be understood that the portion of the yarn 51 moving from the roll 34" to the guide bar 46 is under tension, and that by virtue of the frictional engagement between the roll 34" and the yarn 51, the pull of the winding mechanism effects the rotation of the roll 34" and therewith of the roll 34'. concomitantly, by virtue of the frictional engagement between the roll 34 and the yarn 41, the rotation of that roll effects the movement of the yarn 41 from the roll 18" toward the heating tube 62. As previously stated, however, the diameter of the roll 34" is somewhat smaller than that of the roll 34'. The linear peripheral speed of the yarn 51 passing over the roll 34" thus is less than the linear peripheral speed of the yarn 41 passing over the roll section 34'. As a result, the tension on the plied yarn advancing through the heating and cooling zones of the twist-setting station 7 is relaxed, preferably to a point at which the tension approaches, or is virtually, zero but nevertheless is just sufficient to prevent any substantial slackening and accumulation of yarn either within the tubes 62 and 63 or along the subsequent path up to the roll 34. The plied yarn is, therefore, permitted to contract or shrink longitudinally somewhat while it is being twist-set in the heating zone and then cooled and dried, which enhances the degree of bulk in the final plied yarn 51 as well as its capacity to retain its twist and bulk. The two-section roll 34 may, therefore, be characterized as a shrink roll assembly.

The arrangement according to the present invention thus can be seen to provide a number of advantages in addition to those already set forth herein. For example, since the yarn 51 is substantially dry before it reaches and is wound into the package 49, it does not have to be subjected to those further processing stages, such as skeining, tumbling, prolonged drying, and deskeining operations, which would normally be required in conventional processing of tufting yarns. Moreover, since the yarn has become fully stabilized in its twist-set state by the time it reaches the roll 34", the yarn 51 moving from that roll to the winding station 8 can be subjected to the higher winding tensionwithout risk of damaging the inherent bulk of the twist-set plied yarn. The provision of the shrink roll assembly 34 at the same time ensures that the portion of the yarn moving from the roll 34' through the heating and cooling/drying zones to the roll 34" remains isolated from such higher tension which, if applied to the yarn during this stage, would kill or destroy the inherent bulk.

It will be understood that the foregoing description of a preferred embodiment of the present invention is for purposes of illustration only, and that the various structural and operational features and relationships herein disclosed are susceptible to a number of modifications 7 and changes, none of which entails any departure from the spirit and scope of the present invention as defined in the hereto appendedclaims.

What is claimed is:

1. A method of producing plied, bulked continuous filament yarn, said method comprising, in one continuous operation, the steps of:

a. drawing first and second continuous filament yarns, each having only a producers twist, at equal linear speeds and under tension from respective yarn supplies to a plying station while ballooning one of said yarns about the other;

b. plying said yarns to one another 'at said plying stationso as to form a plied yarn;

c. drawing said plied yarn away from said plying station at a linear speed a predetermined amount greater than that of said first and second yarns for subjecting said plied yarn to a tension greater than the tension on each of said first and second yarns, thereby to maintain a stable balloon;

d. drawing said plied yarn from said plying station and while under a relaxed tension first through a heating zone and then through a cooling and drying zone for twist-setting said plied yarn and enhancing its capacity to retain its resultant twist and bulk; and

e. drawing said twist-set plied yarn under increased tension from said cooling and drying zone to a take-up station for winding said twist-set plied yarn into a package.

2. A method as claimed in claim 1, wherein said plied yarn leaving said plying station is fed into said heating zone at a linear speed greater than the speed at which said twist-set plied yarn is drawn through said cooling and drying zone.

3. A method as claimed in claim 2, wherein said linear feed speed of said plied yarn into said heating zone and said linear feed speed of said twist-set plied yarn away from said cooling and drying zone are predetermined to ensure that the tension on said plied yarn during the twist-setting thereof and on said twist-set plied yarn during the cooling and drying thereof is relaxed to virtually zero, yet is sufficient toprevent any substantial yarn slackening and accumulationinsaid zones.

4. A method as claimed in claim 3, wherein said plied yarn is subjected to moist heat in said heating zone.

5, A method as claimed in claim 3, wherein said plied yarn is subjected to substantially dry heat in said heating zone.

6. A method as claimed in claim 3, wherein the length of the path of movement of said twist-set plied yarn through said cooling and drying zone is sufficiently long to effect both the required cooling of said twist-set plied yarn and the evaporation from the same of any moisture picked up by said plied yarn while in said heating zone.

7. Apparatus for producing plied, bulked continuous filament yarn in one continuous operation, said apparatus comprising:

a. means for drawing first and second continuous filament yams, each having only aproducers twist, at equal linear speeds and under tension from respective yarn supplies to a plying station while ballooning one of said yarns about the other;

b. means for plying said yarns to one another at said plying station so as to form a plied yarn;

0. means for drawing said plied yarn away from said plying station at'a linear speed a predetermined amount greater than that of said first and second yarns for subjecting said plied yarn to a tension greater than the tension on each of said first and second yarns, thereby to maintain a stable balloon;

d. respective means defining a heating zone and a cooling and drying zone for passage of said plied yarn therethrough while being twist-set;

e. means forldrawing said plied'yam from said plying station through said heating zone and said cooling and drying zone and for concurrently relaxing the tension on said plied yarn, for twist-setting said plied yarn and enhancing its capacity to retain its resultant twist and'bulk; and v f. means for drawing said twist-set plied yarn under increased tension from said cooling and drying zone to a take-up station for winding said twist-set plied yarn into a package.

8. Apparatus as claimed in claim 7, wherein said firstnamed drawing means comprises first and second rolls having equal diameters and adapted to have said first and second yarns, respectively, passed at least partially thereabout, each of said first and second rolls having a high friction peripheral surface for slip-free engagement with the respective one of said first and second yarns, and means operatively connected with said rolls for driving the same at equal rotational speeds.

9. Apparatus as claimed in claim 8, wherein said driving means comprises a motor, a hollow spindle driven by said motor, and a pair of gear trains each interconnecting a respective portion of said spindle with an as sociated one of said first and second rolls, said spindle being provided with respective accessopenings to its hollow interior for entry of said first and second yarns thereinto, the portion of said spindle interior at the location of first meeting of said first and second yarns therein constituting said plying station, and the remainder of said spindle interior defining a passageway for movement of said plied yarn away from said plying station.

10. Apparatus as claimed in claim 8, wherein said second-named drawing means comprises a third roll having a diameter greater than the diameter of each of said first and second rolls and adapted to have said plied yarn passed at least partially thereabout subsequent to said plied yarn leaving said plying station, said third roll having a high friction peripheral surface for slip-free engagement with said plied yarn, and means operatively connected with said third roll for driving the same at the same rotational speed as said first and second rolls.

11. Apparatus as claimed in claim 10, wherein said third roll and one of said first and second rolls are respective different diameter sections of a unitary roll structure.

12. Apparatus as claimed in claim 11, wherein said driving means comprises a motor, a hollow spindle driven by said motor, and a pair of gear trains each interconnecting a respective portion of said spindle with an associated one of said first and second rolls, said spindle being provided with respective access openings to its hollow interior for entry of said first and second yarns thereinto, the portion of said spindle interior at the location of first meeting of said first and second yarns therein constituting said plying station, and the remainder of said spindle interior defining a passageway for movement of said plied yarn away from said plying station.

13. Apparatus as claimed in claim 10, wherein said third-named drawing means comprises fourth and fifth rolls the diameter of the former of which is greater than I yarn, respectively, and said fourth and fifth rolls being adapted to rotate at equal rotational speeds.

14. Apparatus as claimed in claim 13, wherein said fourth and fifth rolls are respective different diameter sections of a unitary idler roll structure, and said fourth-named drawing means comprises power-driven take-up means, the rotational speed of said unitary idler roll structure being determined by the linear speed of movement of said twist-set plied yarn engaging said fifth roll.

15. A plied, bulked continuous filament yarn produced by the method of claim 1 and having substantially no pretwist memory in the component single ends of yarn after the plying thereof. 

1. A method of producing plied, bulked continuous filament yarn, said method comprising, in one continuous operation, the steps of: a. drawing first and second continuous filament yarns, each having only a producer''s twist, at equal linear speeds and under tension from respective yarn supplies to a plying station while ballooning one of said yarns about the other; b. plying said yarns to one another at said plying station so as to form a plied yarn; c. drawing said plied yarn away from said plying station at a linear speed a predetermined amount greater than that of said first and second yarns for subjecting said plied yarn to a tension greater than the tension on each of said first and second yarns, thereby to maintain a stable balloon; d. drawing said plied yarn from said plying station and while under a relaxed tension first through a heating zone and then through a cooling and drying zone for twist-setting said plied yarn and enhancing its capacity to retain its resultant twist and bulk; and e. drawing said twist-set plied yarn under increased tension from said cooling and drying zone to a take-up station for winding said twist-set plied yarn into a package.
 2. A method as claimed in claim 1, wherein said plied yarn leaving said plying station is fed into said heating zone at a linear speed greater than the speed at which said twist-set plied yarn is drawn through said cooling and drying zone.
 3. A method as claimed in claim 2, wherein said linear feed speed of said plied yarn into said heating zone and said linear feed speed of said twist-set plied yarn away from said cooling and drying zone are predetermined to ensure that the tension on said plied yarn during the twist-setting thereof and on said twist-set plied yarn during the cooling and drying thereof is relaxed to virtually zero, yet is sufficient to prevent any substantial yarn slackening and accumulation in said zones.
 4. A method as claimed in claim 3, wherein said plied yarn is subjected to moist heat in said heating zone.
 5. A method as claimed in claim 3, wherein said plied yarn is subjected to substantially dry heat in said heating zone.
 6. A method as claimed in claim 3, wherein the length of the path of movement of said twist-set plied yarn through said cooling and drying zone is sufficiently long to effect both the required cooling of said twist-set plied yarn and the evaporation from the same of any moisture picked up by said plied yarn while in said heating zone.
 7. Apparatus for producing plied, bulked continuous filament yarn in one continuous operation, said apparatus comprising: a. means for drawing first and second continuous filament yarns, each having only a producer''s twist, at equal linear speeds and under tension from respective yarn supplies to a plying station while ballooning one of said yarns about the other; b. means for plying said yarns to one another at said plying station so as to form a plied yarn; c. means for drawing said plied yarn away from said plying station at a linear speed a predetermined amount greater than that of said first and second yarns for subjecting said plied yarn to a tension greater than the tension on each of said first and second yarns, thereby to maintain a stable balloon; d. respective means defining a heating zone and a cooling and drying zone for passage of said plied yarn therethrough while being twist-set; e. means for drawing said plied yarn from said plying station through said heating zone and said cooling and drying zone and for concurrently relaxing the tension on said plied yarn, for twist-setting said plied yarn and enhancing its capacity to retain its resultant twist and bulk; and f. means for drawing said twist-set plied yarn under increased tension from said cooling and drying zone to a take-up station for winding said twist-set plied yarn into a package.
 8. Apparatus as claimed in claim 7, wherein said first-named drawing means comprises first and second rolls having equal diameters and adapted to have said first and second yarns, respectively, passed at least partially thereabout, each of said first and second rolls having a high friction peripheral surface for slip-free engagement with the respective one of said first and second yarns, and means operatively connected with said rolls for driving the same at equal rotational speeds.
 9. Apparatus as claimed in claim 8, wherein said driving means comprises a motor, a hollow spindle driven by said motor, and a pair of gear trains each interconnecting a respective portion of said spindle with an associated one of said first and second rolls, said spindle being provided with respective access openings to its hollow interior for entry of said first and second yarns thereinto, the portion of said spindle interior at the location of first meeting of said first and second yarns therein constituting said plying station, and the remainder of said spindle interior defining a passageway for movement of said plied yarn away from said plying station.
 10. Apparatus as claimed in claim 8, wherein said second-named drawing means comprises a third roll having a diameter greater than the diameter of each of said first and second rolls and adapted to have said plied yarn passed at least partially thereabout subsequent to said plied yarn leaving said plying station, said thiRd roll having a high friction peripheral surface for slip-free engagement with said plied yarn, and means operatively connected with said third roll for driving the same at the same rotational speed as said first and second rolls.
 11. Apparatus as claimed in claim 10, wherein said third roll and one of said first and second rolls are respective different diameter sections of a unitary roll structure.
 12. Apparatus as claimed in claim 11, wherein said driving means comprises a motor, a hollow spindle driven by said motor, and a pair of gear trains each interconnecting a respective portion of said spindle with an associated one of said first and second rolls, said spindle being provided with respective access openings to its hollow interior for entry of said first and second yarns thereinto, the portion of said spindle interior at the location of first meeting of said first and second yarns therein constituting said plying station, and the remainder of said spindle interior defining a passageway for movement of said plied yarn away from said plying station.
 13. Apparatus as claimed in claim 10, wherein said third-named drawing means comprises fourth and fifth rolls the diameter of the former of which is greater than that of the latter, said fourth roll being adapted to have said plied yarn leaving said third roll passed at least partly thereabout prior to entry of said plied yarn into said heating zone, said fifth roll being adapted to have said twist-set plied yarn passed at least partly thereabout upon said twist-set plied yarn leaving said cooling and drying zone, each of said fourth and fifth rolls having a high friction peripheral surface for slip-free engagement with said plied yarn and said twist-set plied yarn, respectively, and said fourth and fifth rolls being adapted to rotate at equal rotational speeds.
 14. Apparatus as claimed in claim 13, wherein said fourth and fifth rolls are respective different diameter sections of a unitary idler roll structure, and said fourth-named drawing means comprises power-driven take-up means, the rotational speed of said unitary idler roll structure being determined by the linear speed of movement of said twist-set plied yarn engaging said fifth roll.
 15. A plied, bulked continuous filament yarn produced by the method of claim 1 and having substantially no pretwist memory in the component single ends of yarn after the plying thereof. 